Method for refining dicyclopentadiene

ABSTRACT

A first method for refining dicyclopentadiene of the present invention is characterized in that the method separates and recovers dicyclopentadiene by distilling the crude dicyclopentadiene that contains dicyclopentadiene and is obtained by removing a C5 fraction and a BTX fraction from the reaction product obtained by dimerization reaction of the cracked gasoline by-produced in an ethylene plant that uses as feed stock a C2 fraction, a C3 fraction and a C4 fraction. A second method for refining dicyclopentadiene of the present invention is characterized in that the dicyclopentadiene-containing fraction refined by distillation is brought into contact with an inert gas or a hydrocarbon gas having 1 to 3 carbon atoms.

TECHNICAL FIELD

The present invention relates to a method for refiningdicyclopentadiene.

BACKGROUND ART

Dicyclopentadiene (DCPD), which is represented by the followingstructural formula, is widely used as a starting material for theproduction of compounds such as ethylidene norbornene and cycloolefinpolymer, and refined high-purity DCPD is needed depending on theintended application as the case may be.

Industrially, DCPD is produced by dimerizing cyclopentadiene containedin the C5 fraction of the pyrolysis product of naphtha. In this case, astep of separating the C5 fraction from the pyrolysis product, andfacilities specialized for use for dimerizing the C5 fraction and othersare needed.

As another method, for example, Patent Literature 1 U.S. Pat. No.3,676,509 proposes a method for producing dicyclopentadiene in whichmethod the C8 and higher fractions from a LPG cracking unit arepyrolyzed, and the high-purity cyclopentadiene obtained from thedecomposition products is dimerized to yield dicyclopentadiene.

Additionally, as another method for producing high-purity DCPD, forexample, Patent Literature 2 proposes a method in which cyclopentadienecontained in the C5 fraction obtained by pyrolysis of naphtha isdimerized into dicyclopentadiene, and thereafter, the dicyclopentadienethus obtained is subjected to repeated distillations with a plurality ofdistillation towers.

CITATION LIST Patent Literature

-   Patent Literature 1: U.S. Pat. No. 3,676,509-   Patent Literature 2: Japanese Patent Publication No. 7-39354

SUMMARY OF INVENTION Technical Problem

However, the methods described in U.S. Pat. No. 3,676,509 and JapanesePatent Publication No. 7-39354 both require a huge equipment investmentand a huge operation cost for the purpose of performing the pyrolysisand the dimerization. On the other hand, when high-purity DCPD is used,a satisfactory hue as well as a satisfactory purity is generallyrequired. In consideration of the economic efficiency in the productionof dicyclopentadiene, it is desirable that the number of thedistillation steps is small; however, no examples of the investigationof the methods for improving the hue in such a case have ever beenfound.

Solution to Problem

The present invention has been achieved under the above-describedcircumstances, and an object of the present invention is to provide amethod for refining dicyclopentadiene which method enables to obtainhigh-purity dicyclopentadiene and is more advantageous than conventionalmethods from the aspects of the equipment cost and the operation cost.Another object of the present invention is to provide a method forrefining dicyclopentadiene which method is capable of improving the hueof the dicyclopentadiene-containing fraction refined by distillation.

The present inventors have discovered that high-purity dicyclopentadienecan be separated and recovered by distillation from the specific crudedicyclopentadiene derived from the reaction product obtained bydimerization reaction of a cracked gasoline. Moreover, whileinvestigating a method for obtaining high-purity dicyclopentadiene by asingle distillation from the dicyclopentadiene-containing distillationobject, the present inventors discovered that the color can be removedby bringing a specific gas into contact with the colored fractionseparated by distillation from the top section of the distillationtower, and consequently dicyclopentadiene excellent in hue can beobtained. Additionally, the present inventors have perfected the presentinvention on the basis of these findings.

Specifically, the present invention provides a first method for refiningdicyclopentadiene which method separates and recovers dicyclopentadieneby distilling the crude dicyclopentadiene that containsdicyclopentadiene and is obtained by removing a C5 fraction and a BTXfraction from the reaction product obtained by dimerization reaction ofthe cracked gasoline by-produced in an ethylene plant that uses as feedstock a C2 fraction, a C3 fraction and a C4 fraction.

It is to be noted that in the present specification, a cracked gasolinemeans the C5 to C9 fractions as the by-products obtained from anethylene cracker and additionally, the BTX fraction means the C6 to C8fractions such as benzene, toluene and xylene.

According to the first method for refining dicyclopentadiene, adoptionof the above-described specific crude dicyclopentadiene as adistillation object enables to obtain high-purity refineddicyclopentadiene in a single distillation tower. Additionally, theabove-described crude dicyclopentadiene can be supplied as having passedthrough the separation and recovery of the useful BTX fraction, andhence is advantageous from the viewpoint of the cost of the feed stock.

Additionally, the first method for refining dicyclopentadiene of thepresent invention enables to contribute to the effective use of thecrude dicyclopentadiene that is a by-product in the production of BTXusing a cracked gasoline as feed stock.

In the first method for refining dicyclopentadiene, preferably theabove-described crude dicyclopentadiene contains methyldicyclopentadienein a content of 10 to 40% by mass; and the above-described crudedicyclopentadiene is distilled in such a way that the content ofmethyldicyclopentadiene in the separated and recovered dicyclopentadieneis less than 1.0% by mass. It is to be noted that in the presentspecification, methyldicyclopentadiene (MeDCPD) means a compoundrepresented by the following structural formula.

The reaction product obtained by subjecting a cracked gasoline to adimerization reaction contains as a by-product, a large amount ofmethyldicyclopentadiene; in the refinement of dicyclopentadiene, it isrequired to remove methyldicyclopentadiene contained in a large amount.The refined dicyclopentadiene that is obtained by the above-describedrefining method is capable of being particularly effective for theproduction of ethylidene norbornene or cycloolefin polymer.

Additionally, in the first method for refining dicyclopentadiene of thepresent invention, the content of dicyclopentadiene in theabove-described crude dicyclopentadiene is preferably 40 to 90% by mass,and the above-described crude dicyclopentadiene is preferably distilledin such a way that the purity of the separated and recovereddicyclopentadiene is 93% by mass or more.

Further, in the first method for refining dicyclopentadiene of thepresent invention, the above-described crude dicyclopentadiene ispreferably distilled at 130° C. or lower from the viewpoint of enhancingthe recovery rate of dicyclopentadiene in relation to the crudedicyclopentadiene by suppressing the decomposition of dicyclopentadiene.

The present invention also provides a second method for refiningdicyclopentadiene, wherein a dicyclopentadiene-containing fractionrefined by distillation is brought into contact with an inert gas or ahydrocarbon gas having 1 to 3 carbon atoms.

According to the second method for refining dicyclopentadiene of thepresent invention, the hue of the dicyclopentadiene-containing fractionrefined by distillation can be improved to enable to obtaindicyclopentadiene excellent in hue.

Additionally, the second method for refining dicyclopentadiene of thepresent invention can attain a sufficient hue improvement effect with anapparatus such as a gas-liquid contact apparatus, and hence isadvantageous as compared to a method such as a method using an adsorbentor a method based on crystallization, from the viewpoint of theoperation cost and the equipment cost.

In the second method for refining dicyclopentadiene of the presentinvention, the above-described dicyclopentadiene-containing fractionrefined by distillation is preferably brought into contact with nitrogenor methane. These gases are preferable in that these gases are easilyavailable and easy to handle in petroleum refining plants orpetrochemical plants, and are low in price.

Additionally, in the second method for refining dicyclopentadiene of thepresent invention, the above-described dicyclopentadiene-containingfraction refined by distillation is preferably a product refined bydistillation from the distillation object derived from the reactionproduct obtained by the dimerization reaction of a cracked gasoline. Itis to be noted that in the present specification, a cracked gasolinemeans the C5 to C9 fractions which are by-products obtained from anethylene cracker. On the basis of the fact that the hue of such adicyclopentadiene-containing fraction refined by distillation can beimproved, it is made possible to obtain dicyclopentadiene high in addedvalue, in a larger amount with a satisfactory economic efficiency, fromthe reaction product obtained by dimerization reaction of a crackedgasoline.

Further, in the second method for refining dicyclopentadiene of thepresent invention, the above-described cracked gasoline is preferablythe cracked gasoline by-produced in an ethylene plant that uses as feedstock a C2 fraction, a C3 fraction and a C4 fraction. Also in this case,the hue of the dicyclopentadiene-containing fraction refined bydistillation can be improved, and thus it is made possible to obtaindicyclopentadiene high in added value, in a larger amount with asatisfactory economic efficiency, from the reaction product obtained bydimerization reaction of a cracked gasoline.

Additionally, in the second method for refining dicyclopentadiene of thepresent invention, the above-described dicyclopentadiene-containingfraction refined by distillation preferably contains dicyclopentadienein a content of 85 to 99% by mass, and preferably containscyclopentadiene and methylcyclopentadiene in a sum content of 0.1 to 10%by mass. According to the present invention, also from such a fraction,dicyclopentadiene from which light impurities such as cyclopentadieneand methylcyclopentadiene are sufficiently removed and which isexcellent in hue can be obtained. In this case, from the remainingfraction from which higher-purity dicyclopentadiene has been extracted,useful dicyclopentadiene can be recovered efficiently, and thus it ismade possible to further improve the economic efficiency in theproduction of dicyclopentadiene.

Additionally, in the second method for refining dicyclopentadiene of thepresent invention, the hue of the above-describeddicyclopentadiene-containing fraction refined by distillation exceeds100 in terms of APHA, and the hue concerned can be made to be 100 orless in terms of APHA.

Advantageous Effects of Invention

According to the present invention, high-purity dicyclopentadiene can beobtained, and additionally, a method for refining dicyclopentadiene,more advantageous than conventional methods from the viewpoint of theequipment cost and the operation cost, can be provided. Also accordingto the present invention, a method for refining dicyclopentadienecapable of improving the hue of the dicyclopentadiene-containingfraction refined by distillation can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart illustrating an example of a refining apparatusof dicyclopentadiene for embodying a first method for refiningdicyclopentadiene of the present invention;

FIG. 2 is a flow chart illustrating another example of a refiningapparatus of dicyclopentadiene for embodying the first method forrefining dicyclopentadiene of the present invention;

FIG. 3 is a flow chart illustrating an example of a refining apparatusof dicyclopentadiene for embodying a second method for refiningdicyclopentadiene of the present invention; and

FIG. 4 is a flow chart illustrating another example of a refiningapparatus of dicyclopentadiene for embodying the second method forrefining dicyclopentadiene of the present invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, a preferred embodiment of the present invention isdescribed in detail with reference to the accompanying drawings. It isto be noted that in the description of the drawings, the same symbolsare used for the same components or the corresponding components, andrepetitive explanations are omitted.

FIG. 1 is a flow chart illustrating an example of a refining apparatusof dicyclopentadiene for embodying a first method for refiningdicyclopentadiene of the present invention. A refining apparatus 100illustrated in FIG. 1 is provided with a distillation tower 10 todistill a specific crude dicyclopentadiene according to the first methodfor refining dicyclopentadiene of the present invention. To thedistillation tower 10, a recovery line L2 to recover thedicyclopentadiene separated by distillation and a recovery line L3 totake out the fraction in the tower bottom are connected.

The specific crude dicyclopentadiene according to the first method forrefining dicyclopentadiene of the present invention, fed to thedistillation tower 10 is a product obtained by removing a C5 fractionand a BTX fraction from the reaction product obtained by dimerizationreaction of the cracked gasoline by-produced in an ethylene plant thatuses as feed stock a C2 fraction, a C3 fraction and a C4 fraction. It isto be noted that an ethylene plant that uses as feed stock a C2fraction, a C3 fraction and a C4 fraction is referred to as a LPGcracker as the case may be.

The cracked gasoline is only required to contain C5 to C9 fractions;however, for the purpose of reducing impurities similar todicyclopentadiene, the cracked gasoline is preferably a product in whichthe sum of the contents of isoprene and piperylene is equal to or lessthan half the content of cyclopentadiene.

Additionally, as the above-described reaction product, for example,there can be used a product obtained by subjecting the above-describedcracked gasoline to a dimerization reaction under the liquid phasereaction conditions in which the reaction temperature is 75° C. to 200°C.

In the present embodiment, the residual obtained by removing bydistillation the unreacted C5 fraction from the above-described reactionproduct, and by further removing by distillation the BTX fraction, canbe used as it is as the crude dicyclopentadiene according to the presentinvention.

The unreacted C5 fraction can be removed by a usual refinement bydistillation. Additionally, the BTX fraction can be removed by a usualrefinement by distillation.

Additionally, in the crude dicyclopentadiene fed to the distillationtower 10, for the purpose of making the purity of the obtained product,dicyclopentadiene, be 93% by mass or more, the sum content ofisopropenylnorbornene (IPNB) and propenylnorbornene (PNB) is preferablyless than 4% by mass and more preferably less than 3% by mass in a ratioin relation to dicyclopentadiene.

It is to be noted that there is a possibility thatmethyltetrahydroindene (MeTHI), methyldicyclopentadiene (MeDCPD) and thelike are contained in the crude dicyclopentadiene in addition toisopropenylnorbornene (IPNB) and propenylnorbornene (PNB). Thesecompounds respectively refer to the compounds represented by thefollowing structural formulas.

TABLE 1

As the distillation tower 10, a heretofore known distillation tower canbe used. In the distillation tower 10, the above-described crudedicyclopentadiene can be separated, for example, into a first fraction(a fraction having a boiling points of 160 to 170° C. under normalpressure) that contains dicyclopentadiene in a high concentration, and asecond fraction (a fraction having a boiling point of 172° C. or higher)that contains heavy impurities such as MeTHI and MeDCPD and is heavierthan the first fraction. The first fraction is recovered through therecovery line L2 as refined dicyclopentadiene. The second fraction isrecovered from the tower bottom through the recovery line L3, and can beused, for example, as a liquid fuel. Additionally, a light fraction thatcontains light impurities such as cyclopentadiene (CPD) andmethylcyclopentadiene (MeCPD) and is lighter than the first fraction canbe recovered separately, and can be used as a dicyclopentadiene recoverysource or a gas fuel by preferably being made to pass through abelow-described refining method.

The theoretical number of stages of the distillation tower 10 can be setat 30 to 60, and preferably at 40 to 50 from the viewpoint of theoptimization of the relation between the reflux ratio and the number ofdistillation stages. However, the optimal number of stages is varieddepending on the composition, and hence can be appropriately altered.

Additionally, the distillation in the distillation tower 10 ispreferably performed at a temperature of 130° C. or lower, from theviewpoint of increasing the recovery ratio of dicyclopentadiene relativeto the crude dicyclopentadiene by suppressing the decomposition ofdicyclopentadiene. It is to be noted that the temperature as referred toherein means the temperature at the tower bottom.

Further, the distillation in the distillation tower 10 is preferablyperformed under the conditions that the pressure at the tower top is 10to 15 kPaA, the temperature at the tower top is 90 to 105° C., and thetemperature at the tower bottom is 120 to 135° C., with a reflux ratioof 4 to 8, preferably 6 to 7.

In the present embodiment, a material containing dicyclopentadiene in acontent of 40 to 90% by mass is prepared as the above-described crudedicyclopentadiene, and such a crude dicyclopentadiene is preferablydistilled in such a way that the first fraction contains DCPD in acontent of 93% by mass or more, and more preferably 95% by mass or more.Such distillation can be performed, for example, by controlling thereflux ratio in the distillation tower 10 or the recovery ratio ofdicyclopentadiene in the distillation tower 10.

Additionally, in the case where the above-described crudedicyclopentadiene contains methyldicyclopentadiene in a content of 10 to40% by mass, the above-described crude dicyclopentadiene is preferablydistilled in such a way that the content of methyldicyclopentadiene inthe above-described first fraction is less than 1.0% by mass. Suchdistillation can be performed, for example, by controlling the refluxratio in the distillation tower 10 or the recovery ratio ofdicyclopentadiene in the distillation tower 10.

Further, in the present embodiment, the first fraction can be taken outfrom the side of the distillation tower by distilling theabove-described crude dicyclopentadiene under the conditions thatside-cutting is performed from an optional position in the range fromthe tower top to the feed stage. In the sense of rendering thedistillation efficient, preferably the above-described crudedicyclopentadiene is distilled under the conditions that side-cutting isperformed at a position downward by 3 to 10 stages from the tower top,and the first fraction is taken out from the side of the distillationtower. In this case, the content of DCPD in the first fraction can befurther improved, and at the same time, the hue of the first fractioncan be made more excellent. In this case, as described above, the lightfraction that is obtained from the tower top, contains light impuritiessuch as cyclopentadiene (CPD) and methylcyclopentadiene (MeCPD) and islighter than the first fraction can be recovered separately, and can beused as a dicyclopentadiene recovery source or a gas fuel preferably bybeing made to pass through a below-described refining method.

FIG. 2 is a flow chart illustrating an example of a method for takingout the first fraction from the side of the distillation tower in thefirst method for refining dicyclopentadiene of the present invention. Inthe refining apparatus 110 shown in FIG. 2, L22 is a line to take outthe first fraction from the side of the distillation tower 10 and L21 isa line to take out the light fraction from the tower top.

FIG. 3 is a flow chart illustrating an example of a refining apparatusof dicyclopentadiene for embodying a second method for refiningdicyclopentadiene of the present invention. The refining apparatus 120shown in FIG. 3 is provided with a distillation tower 10 to distill adistillation object that contains dicyclopentadiene and a distillationtower 20 to bring the dicyclopentadiene-containing light fractionrefined by distillation in the distillation tower 10 into contact withan inert gas or a hydrocarbon gas having 1 to 3 carbon atoms. To thedistillation tower 10, a feed line L1 to feed to the distillation tower10 the distillation object that contains dicyclopentadiene is connected.The distillation tower 10 and the distillation tower 20 are connected toeach other with a transfer line L21, and thedicyclopentadiene-containing light fraction refined by distillation inthe distillation tower 10 is fed to the distillation tower 20 throughthe transfer line L21. Further, connected to the distillation tower 10is a recovery line L22 to take out the firstdicyclopentadiene-containing fraction refined by distillation in thedistillation tower 10. Additionally, connected to the distillation tower20 are a feed line L4 to feed to the distillation tower 20 an inert gasor a hydrocarbon gas having 1 to 3 carbon atoms, a recovery line L5 totake out from the distillation tower 20 a dicyclopentadiene-containingliquid improved in hue and a recovery line L6 to take out the lightfraction from the distillation tower 20. Thus, in the distillation tower20, the second method for refining dicyclopentadiene of the presentinvention is embodied.

As the dicyclopentadiene-containing distillation object fed from L1,there can be used a product derived from the reaction product obtainedby dimerization reaction of a cracked gasoline, or adicyclopentadiene-containing liquid that contains as impurities lighterfractions than dicyclopentadiene such as cyclopentadiene ormethylcyclopentadiene.

From the viewpoint that high-purity dicyclopentadiene is efficientlyobtained by a single distillation from the recovery line L22, thedistillation object is preferably a product derived from the reactionproduct based on the dimerization reaction of a cracked gasoline. It isto be noted that the cracked gasoline as referred to herein means the C5to C9 fractions that are by-products in an ethylene cracker. Also fromthe same viewpoint, the cracked gasoline is preferably a productobtained from a LPG cracker. It is also to be noted that a LPG crackermeans an ethylene cracker that uses as feed stock a C2 fraction, a C3fraction and a C4 fraction.

Further, in the present embodiment, preferably fed as theabove-described distillation object to the distillation tower 10 is aproduct obtained by removing the unreacted C5 fraction and the unreactedBTX fraction from the reaction product obtained by dimerization reactionof the cracked gasoline obtained from a LPG cracker. The unreacted C5fraction and the unreacted BTX fraction can be respectively removed by ausual refinement by distillation.

In the above-described distillation object, the sum content ofisopropenylnorbornene (IPNB) and propenylnorbornene (PNB) is preferablya proportion of 4% by mass or less in relation to dicyclopentadiene.

It is to be noted that there is a possibility thatmethyltetrahydroindene (MeTHI), methyldicyclopentadiene (MeDCPD) and thelike are contained in the above-described distillation object derivedfrom the reaction product, in addition to isopropenylnorbornene (IPNB)and propenylnorbornene (PNB). These compounds respectively refer to thecompounds represented by the above-described structural formulas inTable 1.

As the distillation tower 10, a heretofore known distillation tower canbe used. In the distillation tower 10, the above-described distillationobject is separated, for example, into the light fraction that containslight impurities such as cyclopentadiene (CPD) and methylcyclopentadiene(MeCPD) and contains dicyclopentadiene, the first fraction that containsdicyclopentadiene in a high concentration and the second fraction (afraction having a boiling point of 172° C. or higher) that containsheavy impurities such as MeTHI and MeDCPD. The light fraction thatcontains light impurities such as CPD and MeCPD and containsdicyclopentadiene is transferred to the distillation tower 20 throughthe transfer line L21, and the first fraction that containsdicyclopentadiene in a high concentration is recovered as a productthrough the recovery line L22.

The theoretical number of stages of the distillation tower 10 can be setat 30 to 60, and preferably at 40 to 50 from the viewpoint of theoptimization of the relation between the reflux ratio and the number ofdistillation stages. However, the optimal number of stages is varieddepending on the composition, and hence can be appropriately altered.Additionally, the distillation in the distillation tower 10 ispreferably performed under the conditions that the pressure at the towertop is 10 to 15 kPaA, the temperature at the tower top is 90 to 105° C.,and the temperature at the tower bottom is 120 to 135° C., with a refluxratio of 4 to 8, preferably 6 to 7.

In the present embodiment, the above-described distillation object isdistilled in such a way that the light fraction contains DCPD preferablyin a content of 80 to 99% by mass and more preferably in a content of 85to 95% by mass.

Additionally, in the present embodiment, the first fraction is taken outfrom the side of the distillation tower by distilling theabove-described distillation object under the conditions thatside-cutting is performed from an optional position in the range fromthe tower top to the feed stage. In the sense of rendering thedistillation efficient, preferably the above-described distillationobject is distilled under the conditions that side-cutting is performedat a position downward by 3 to 10 stages from the tower top, and thefirst fraction is taken out from the side of the distillation tower. Inthis case, it is preferable to perform the distillation in such a waythat the content of dicyclopentadiene in the first fraction thatcontains dicyclopentadiene in a high concentration is 93% by mass ormore and the content of MeDCPD is less than 1.0% by mass. Additionally,it is preferable to refine, in the distillation tower 20, the lightfraction that is obtained from the tower top under the above-describedconditions and contains light impurities such as CPD and MeCPD andcontains dicyclopentadiene. In this case, the hue of the first fractionobtained as a high-purity DCPD product can be made more excellent, andat the same time, from the light fraction, DCPD improved in hue by thesecond refining method of the present invention can be sufficientlyobtained.

When distillation is performed with reference to the hue of the lightfraction, the hue of the light fraction usually exceeds 100 in terms ofAPHA; however, the hue of the light fraction may be 200 or more. It isto be noted that APHA is measured by the color measurement methodspecified in ASTM D1209. Also in this case, the hue of the firstfraction obtained as a high-purity DCPD product can be made moreexcellent, and at the same time, from the light fraction, DCPD improvedin hue by the second refining method of the present invention can besufficiently obtained.

In the distillation tower 20, the second method for refiningdicyclopentadiene of the present invention is embodied. In the presentembodiment, a distillation tower that is a packed tower is used;however, a vessel that permits gas-liquid contact and permits taking-outof a predetermined liquid can be used without any limitation. Examplesof such a vessel include a distillation tower that is a tray tower.

The theoretical number of stages of the distillation tower 20 ispreferably set at 10 to 30, and more preferably at 15 to 25 from theviewpoint of efficient separation. However, the optimal number of stagesis varied depending on the composition, and hence can be appropriatelyaltered. In the present embodiment, the light fraction can be fed fromthe tower top of the distillation tower 20 and an inert gas or ahydrocarbon gas having 1 to 3 carbon atoms can be fed from the towerbottom of the distillation tower 20.

As the inert gas, nitrogen, argon or carbon dioxide can be used. As thehydrocarbon gas having 1 to 3 carbon atoms, methane, ethane or propanecan be used. In the present embodiment, because of easy availability oreasy handleability, nitrogen, methane or ethane is preferable, andnitrogen or methane is more preferable.

The contact of the light fraction with the inert gas or the hydrocarbongas having 1 to 3 carbon atoms can be performed at normal temperatureunder normal pressure; for the purpose of more efficiently removinglight impurities such as CPD and MeCPD, preferably the light fraction ispreheated at 60 to 90° C., and then fed to the distillation tower 20.

The flow rate of the light fraction and the flow rate of the inert gasor the hydrocarbon gas having 1 to 3 carbon atoms into the distillationtower 20 are preferably set in such a way that the volume ratio of theabove-described gas to the light fraction is 50 to 200.

By passing through the above-described gas-liquid contact step, from thedistillation tower 20, a dicyclopentadiene-containing liquid that isimproved in hue and contains a high-purity dicyclopentadiene isrecovered through the recovery line L5. In the present embodiment, thehue of the dicyclopentadiene-containing liquid is preferably 100 or lessin terms of APHA, and more preferably 60 or less in terms of APHA.

FIG. 4 is a flow chart illustrating another example of a refiningapparatus of dicyclopentadiene for embodying the second method forrefining dicyclopentadiene of the present invention. The refiningapparatus 130 of dicyclopentadiene shown in FIG. 4 has the sameconfiguration as the refining apparatus 120 of dicyclopentadiene exceptthat the refining apparatus 130 of dicyclopentadiene shown in FIG. 4 isnot provided with the recovery line L22 in the refining apparatus 120 ofdicyclopentadiene.

In the present embodiment, the fraction that has been refined bydistillation in the distillation tower 10 and contains dicyclopentadieneis refined in the distillation tower 20 by the second method forrefining dicyclopentadiene of the present invention.

Also in the refining apparatus 130 of dicyclopentadiene, the refinementof dicyclopentadiene can be performed under the same conditions as inthe refining apparatus 120 of dicyclopentadiene except that thetaking-out of the first fraction is omitted.

The distillation in the distillation tower 10 is preferably performedunder the conditions that the pressure at the tower top is 10 to 15kPaA, the temperature at the tower top is 90 to 105° C., and thetemperature at the tower bottom is 120 to 135° C., with a reflux ratioof 4 to 8, preferably 6 to 7.

In the present embodiment, the above-described distillation object fedthrough L1 is distilled in such a way that the above-described fractionthat is taken out from L21 and contains dicyclopentadiene contains DCPDpreferably in a content of 80 to 99% by mass, and more preferably in acontent of 85 to 95% by mass. In this case, a DCPD product that is highin purity and excellent in hue can be efficiently obtained by therefinement and the refinement by distillation in the distillation tower20, according to the second refining method of the present invention.

Additionally, the hue of the dicyclopentadiene-containing fraction takenout from the above-described L21 usually exceeds 100 in terms of APHA;however, the hue of the concerned fraction may be 200 or more. Also inthis case, a DCPD product that is high in purity and excellent in huecan be efficiently obtained by the refinement and the refinement bydistillation in the distillation tower 20, according to the secondrefining method of the present invention.

The preferred embodiment of the present invention has been describedabove in detail; however, the present invention is not limited to theabove-described embodiment, and may be replaced with other embodiments.For example, in another embodiment, the refining method may be alteredto a method in which the purity of dicyclopentadiene is stepwiseenhanced by twice performing the distillation, instead of increasing thetheoretical number of stages or the reflux ratio in the distillationtower 10.

According to the method for refining dicyclopentadiene of the presentinvention, by preparing a specific crude dicyclopentadiene, ahigh-purity dicyclopentadiene can be obtained by performing a singledistillation with common distillation equipment. Additionally, thepresent invention can provide an industrially advantageous method forproducing dicyclopentadiene in which method a high-puritydicyclopentadiene is obtained from LPG. In other words, the concernedmethod for producing dicyclopentadiene includes: a first step ofpreparing the cracked gasoline by-produced in an ethylene plant thatuses as feed stock a C2 fraction, a C3 fraction and a C4 fraction; asecond step of subjecting the cracked gasoline prepared in the firststep to a dimerization reaction; a third step of obtaining a crudedicyclopentadiene by removing a C5 fraction and a BTX fraction from thereaction product obtained in the second step; and a fourth step ofseparating and recovering dicyclopentadiene by distilling the crudedicyclopentadiene obtained in the third step. The second to fourth stepscan be performed under the above-described conditions.

Additionally, the method for refining dicyclopentadiene according to thepresent invention which method includes a step of bringing thedicyclopentadiene-containing fraction that is refined by distillationinto contact with an inert gas or a hydrocarbon gas having 1 to 3 carbonatoms can be used, for example, as a method for improving the hue of thedicyclopentadiene-containing fraction colored due to a trace amount oflight impurities or a method for removing light impurities from adicyclopentadiene-containing fraction in which the separation and theremoval of light impurities are incomplete.

EXAMPLES

Hereinafter, the present invention is described in detail with referenceto Examples, but the present invention is not limited by these Examples.

Example 1

A crude dicyclopentadiene having the composition shown in Table 2 wasprepared, wherein the crude dicyclopentadiene was obtained by removing aC5 fraction and a BTX fraction from the reaction product obtained bydimerization reaction of the cracked gasoline by-produced in a LPGcracker.

To a distillation tower (having a theoretical number of stages of 40) ofa refining apparatus having the same configuration as the configurationof the refining apparatus 100 shown in FIG. 1, the above-described crudedicyclopentadiene preheated to 80° C. was fed at a flow rate of 40g/min, and the pressure and the reflux ratio at the tower top were setat 12.5 kPaA and 8, respectively. The flow rate of a first fractionrecovered from the tower top was 25 g/min and the hue of this fractionwas 200+ in terms of APHA. Additionally, a second fraction was recoveredfrom the tower bottom at a flow rate of 15 g/min. In this case, thetower top temperature was 99° C. and the tower bottom temperature was118° C.

The compositions of the obtained first and second fractions are shown inTable 2. The composition analysis was performed with a gaschromatograph.

TABLE 2 Fed crude First Second dicyclopentadiene fraction fraction CPD(% by mass) 0.1 0.3 0.0 MeCPD (% by mass) 0.0 0.1 0.0 IPNB and PNB (% bymass) 2.5 3.9 0.00 DCPD (% by mass) 72.4 95.0 37.0 MeTHI (% by mass) 2.70.7 5.7 MeDCPD (% by mass) 16.3 0.00 40.2 Others (heavy fraction) 4.30.0 13.8 (% by mass)

Example 2

To a distillation tower (having a theoretical number of stages of 20) ofa refining apparatus having the same configuration as the configurationof the refining apparatus 110 shown in FIG. 2, the above-described crudedicyclopentadiene preheated to 80° C. was fed at a flow rate of 100g/min, and the pressure and the reflux ratio at the tower top were setat 12.5 kPaA and 40, respectively. A first fraction was taken out byside-cutting at a position of the fifth stage from the tower top, andwas recovered at a flow rate of 66 g/min. The recovery flow rate of alight fraction from the tower top was 8 g/min, and a second fraction wasrecovered from the tower bottom at a flow rate of 26 g/min. In thiscase, the tower top temperature was 103° C., and the tower bottomtemperature was 124° C. The content of dicyclopentadiene in the firstfraction was found to be 93.3% by mass, and the hue of the firstfraction was 60 in terms of APHA.

Example 3

A dicyclopentadiene-containing fraction having a composition shown inTable 3 was prepared, wherein the dicyclopentadiene-containing fractionwas obtained by refinement by distillation from a fraction obtained byremoving a C5 fraction and a BTX fraction from the reaction productobtained by dimerization reaction of the cracked gasoline by-produced ina LPG cracker. The hue of this dicyclopentadiene-containing fraction was200+ in terms of APHA.

To a distillation tower having a theoretical number of stages of 10, theabove-described dicyclopentadiene-containing fraction preheated to 65°C. was fed from the tower top at a flow rate of 200 ml/min, nitrogen wasfed from the tower bottom at a flow rate of 2.6 L/h, and thus agas-liquid contact was performed. Thus, a recovered fraction wasobtained at a flow rate of 198 ml/min. The hue of this recoveredfraction was about 50 in terms of APHA. Additionally, it was verifiedthat in the recovered fraction, as shown in Table 3, the contents of CPDand MeCPD were reduced while the content of DCPD was being sufficientlymaintained. The composition analysis was performed with a gaschromatograph.

TABLE 3 Fed dicyclopentadiene- Recovered containing fraction fractionCPD (% by mass) 0.16 0.01 MeCPD (% by mass) 0.12 0.00 IPNB (% by mass)2.07 2.17 PNB (% by mass) 1.14 1.20 DCPD (% by mass) 94.77  94.60 MeTHI(% by mass) 0.32 0.78 MeDCPD (% by mass) 1.37 1.24 Others (% by mass)0.05 0.00 Hue (APHA) 200+    About 50

Example 4

A dicyclopentadiene-containing fraction having the composition shown inTable 4 was prepared by distillation from the same distillation objectas in Example 3. The hue of this dicyclopentadiene-containing fractionwas 200+ in terms of APHA.

To a distillation tower having a theoretical number of stages of 20, theabove-described dicyclopentadiene-containing fraction preheated to 90°C. was fed from the tower top at a flow rate of 310 L/h, methane was fedfrom the tower bottom at a flow rate of 35 kg/h, and thus a gas-liquidcontact was performed. Thus, a recovered fraction was obtained at a flowrate of 300 L/h. The hue of this recovered fraction was 50 in terms ofAPHA. Additionally, it was verified that in the recovered fraction, asshown in Table 4, the content of DCPD was large, and the contents of CPDand MeCPD were reduced.

TABLE 4 Fed dicyclopentadiene- Recovered containing fraction fractionCPD (% by mass) 1.0 0.0 MeCPD (% by mass) 1.7 0.02 IPNB and PNB (% bymass) 4.2 4.3 DCPD (% by mass) 93.0  95.5 Others (% by mass) 0.1 0.1 Hue(APHA) 200+   50

DESCRIPTION OF SYMBOLS

10 . . . Distillation tower; 20 . . . Distillation tower; 100, 110, 120,130 . . . Refining apparatus of dicyclopentadiene

The invention claimed is:
 1. A method for distilling dicyclopentadieneconsisting essentially of: distilling a crude dicyclopentadiene, whichcomprises 10 to 40% by mass methyl dicyclopentadiene, once to obtain atleast a first fraction comprising a separated and recovereddicyclopentadiene, which comprises less than 1.0% by mass methyldicyclopentadiene, and a second fraction that is heavier than the firstfraction wherein the crude dicyclopentadiene is obtained by removing aC5 fraction and a BTX fraction from a reaction product obtained byperforming a dimerization reaction on a cracked gasoline by-produced inan ethylene plant that uses as a feedstock a C2 fraction, a C3 fractionand a C4 fraction.
 2. The method for distilling dicyclopentadieneaccording to claim 1, wherein: the content of dicyclopentadiene in thecrude dicyclopentadiene is 40 to 90% by mass; and the crudedicyclopentadiene is distilled in such a way that the purity of theseparated and recovered dicyclopentadiene is 93% by mass or more.
 3. Themethod for distilling dicyclopentadiene according to claim 1, whereinthe crude dicyclopentadiene is distilled at 130° C. or lower.
 4. Themethod for distilling dicyclopentadiene according to claim 1, whereinthe crude dicyclopentadiene is distilled over 30 to 60 stages of thetheoretical number of stages.
 5. The method for distillingdicyclopentadiene according to claim 2, wherein the crudedicyclopentadiene is distilled at 130° C. or lower.
 6. The method fordistilling dicyclopentadiene according to claim 2, wherein the crudedicyclopentadiene is distilled over 30 to 60 stages of the theoreticalnumber of stages.
 7. The method for distilling dicyclopentadieneaccording to claim 3, wherein the crude dicyclopentadiene is distilledover 30 to 60 stages of the theoretical number of stages.
 8. The methodfor distilling dicyclopentadiene according to claim 2, wherein the crudedicyclopentadiene is distilled at 130° C. or lower and over 30 to 60stages of the theoretical number of stages.
 9. The method for distillingdicyclopentadiene according to claim 1, wherein the cracked gasolineby-product by-produced in an ethylene plant that uses as a feedstock aC2 fraction, a C3 fraction and a C4 fraction comprises isoprene andpiperylene and the sum of these two components is half or less than halfof an amount of cyclopentadiene contained in the by-product.
 10. Themethod for distilling dicyclopentadiene according to claim 1, whereinthe reaction product is obtained by performing the dimerization reactionunder liquid-phase reaction conditions at a temperature of from 75° C.to 200° C.
 11. The method for distilling dicyclopentadiene according toclaim 1, wherein the sum content of isopropenylnorbornene andpropenylnorborene in the crude dicyclopentadiene is less than 4% by massin relation to dicyclopentadiene content.